Drive unit for rotatable signs

ABSTRACT

A drive unit for a rotatable sign, preferably electrically illuminated, which is mounted on the top of a supporting post. The post is hollow and houses and supports the drive unit in the upper end thereof. The drive unit comprises (1) a sign rotating shaft journaled in the hollow support with the upper end adapted to be secured to the sign, (2) a speed reducing mechanism having an output shaft and an input shaft, (3) an electrical motor mounted in the hollow support below the speed reduction mechanism and having a shaft and means, preferably a rubber connector, operatively connecting the motor shaft to the input shaft of the speed reduction mechanism, and (4) means operatively connecting the output shaft of the speed reduction mechanism to the sign rotating shaft, preferably a flexible connection including universal joints and a friction clutch. The axes of rotation of all said shafts are in substantial alignment. Electric power is supplied (a) to the motor by conductors passing up the supporting post and (b) to a commutator comprising brushes mounted in the hollow support and slip rings mounted on and insulated from the sign rotating shaft through which electrical conductors pass from the slip rings upwardly into the sign to provide the illumination.

U Q I United States Patent 1 1 7 Bevan [4 1 May 9, 1972 54 DRIVE UNIT FOR ROTATABLE SIGNS 57 ABSTRACT [72] inventor: James W. Bevan, PO. Box 2515, Salt A drive unit for a rotatable sign, preferably electrically illu- Lake City, Utah 84110 minated, which is mounted on the top of a supporting post. The post is hollow and houses and supports the drive unit in [22] F'lgd: 1969 the upper end thereof. The drive unit comprises (i) a sign [21] AWL 889,148 rotating shah journaled in the hollow support with the upper end adapted to be secured to the sign, (2) a speed reducing mechanism having an output shaft and an input shaft, (3) an [52] U.S;Cl ..40/33, 74/801, 318/47, electrical motor mounted in the hollow support below the 9 /351 speed reduction mechanism and having a shaft and means, [51] Int.Cl. ..G09f11/02,Fl6h l/28,Fl6h 67/00 preferably a rubber connector, operatively connecting the [58] Field of Search ..40/3 3; 74/801 motor shaft to the input shaft of the speed reduction mechanism, and (4) means operatively connecting the output [56] References Cited shaft of the speed reduction mechanism to the sign rotating shaft, preferably a flexible connection including universal UNITED STATES PATENTS jointsand a friction clutch. The axes of rotation of all said I shafts are in substantial alignment. Electric power is supplied g (a) to the motor by conductors passing up the supporting post 3427738 2/1969 :32: 40/33 and (b) to a commutator comprising brushes mounted in the 3,453,906 7/l969 1m ..74/80l and sup '"sulated mm Primary Examiner-Arthur J. McKeon AItorney-George H. Mortimer e' it the sign rotating shaft through which electrical conductors pass from the slip rings upwardly into the sign to provide the illumination.

12 Claims, 7 Drawing Figures PATENTEDMAY 9 I972 SHEET 3 [1F 3 FIG.7

BACKGROUND OF THE INVENTION In recent years there has been an increasing demand for and use of large mobile display signsnsuch signs are widely used at automobile service stations, shopping centers, stores, banks andother businesses and are made movable so as to attract attention. In general they are mounted at the top of a supporting structure, usually a hollow post, and are rotated around a vertical axis. They are usually quite large in size and are commonly visible and readable day and night at a considerable distance.

Many different forms of rotating mechanisms for such signs have been proposed and tried. Reference is made to US. Pat. No. 3,427,728 granted Feb. 18, 1969 which discloses and claims an invention of the inventor of the device disclosed and claimed herein and to the description of the prior art contained therein. The drive unit disclosed in said patent has functioned satisfactorily in large rotatable signs used by a number of the large oil companies in the United States. This drive unit is housed in the illuminated sign and rotates around a fixed shaft at the top of the supporting structure. When inspection and repair of the unit is required, it has been necessary to remove part of the sign to gain access to the drive unit and this has caused difliculty during windy weather when the sign can rotate in a stiff wind and some repairmen have been injured on such occasions.

SUMMARY OF THE INVENTION The present invention relates to an improved drive unit for rotatable signs which overcomes the problems of the prior art in that it is housed in the upper end of the supporting structure, preferably a hollow supporting post, in which a sign rotating shaft is journaled. The sign is adapted to be secured to the exposed upper end of this shaft through which electrical connections may pass from slip rings for illuminating the sign, where illumination is desired. Also mounted in the hollow support is the drive motor having a shaft which is operatively connected through a speed reduction mechanism and, preferably, a friction clutch to the sign rotating shaft. The axes of rotation of the rotating parts of all of these mechanisms are'substantially aligned so as to permit the entire drive unit to be housed in a hollow post of acceptable dimensions. The conductors to carry electric power to the motor are brought from a suitable source up through the hollow supporting post. If the sign is to be illuminated a suitable commutator including brushes and slip rings may be provided for-supplying the electrical power BRIEF DESCRIPTION OF THE DRAWING Reference is had to the drawing's in connection with the following detailed description of the invention'in which:

FIG. 1 is an elevation of'a drive unit for a rotatable sign mounted in a hollow supporting post, the post and sign being shown fragmentarily;

FIG. 2 is a perspective view, on a larger scale, of the sign rotating shaft assembly as seen from above, the assembly being secured in the upper end of the supporting post which is broken away to show structure of the unit;

FIG. 3 is a fragmentary orthometric view of the lower part of the sign rotating shaft, a friction clutch, a flexible connector, the speed reduction mechanism and part of the motor with some parts broken away and in section to show internal structure;

FIG. 4 is a vertical section of a part of the sign rotating shaft to show the slip ring and brush structure;

FIG. 5 is a top plan view, of ,the mounting frame for the motor and speed reducer installed in the post; and

FIG. 6 is a schematic internal, view of a speed reducing mechanism utilizing sun and planet gears; and

FIG. 7 is a perspective of a cycloidal speed reducing mechanism with parts broken away to show internal structure,

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring first to FIG. I, an elongated. hollow support 1 has a sign rotating shaft 2 journaledin the upper end thereof with the upper end of the shaft extending beyond the support for connection with a rotatingsign 3. The sign itself forms no part of the present invention and it may have any desired structure, shape and design and may be illuminated or not as desired, If the sign is illuminated, a slip ring-brush assembly 4, is provided to supply the electrical energy from fixed electrical conductors in the hollowsupport-through the sign rotating shaft and into the sign. Also mounted in the hollow support is an electrical motor 5 having a shaft, for driving a speed reducing mechanism 6 which is operatively connected to the sign rotating shaft 2. Preferably this operative connection includes a friction clutch 7 or torque limiter and a flexible connecting means Bwhich makes it unnecessary to have perfect alignment of the speed reducing mechanism with the sign rotating shaft. The friction clutch is a preferred but not essential part of the drive unit if the speed reduction mechanism is of the preferred epitrochoid planet gear-circular (pin) tooth sun gear combination type and the electric motor has built in thermalprotection with automatic reset, as will be more fully explained hereinafter. An access door 9 is provided in the hollow support.

Generally speaking, the elongated hollow support I will rest on a cement foundation 10 and will be a single supporting post 12 of any desired shape in cross-section, e.g., circular, rectangular, hexagonal, octagonal 'orcruciform as shown in FIG. 2, which is a preferred cross-sectional shape of supporting post. It is provided with asuitable flange base I4 for anchoring the post to the cement foundation by means of bolts 16. A cap 18 is provided to prevent ingress of water into the interior of the post and it may comprise a top plate 20 with a depending flange 22' extending down along and conformingin shape to the supportingpost. The top 20 isprovided with a central opening for apurpose soon to be. described.

The. sign rotating shaft 2 has an upper portion 24 of sufficient diameter and strength to withstand the stresses imposed on it by the sign and .drive mechanism. Itis joumaled in the upper end of the supporting post bya pair of ball or roller bearings 26 each of which includes a hub 28 and a flange 30.

Referring now to FIG. 2, it will be seen that the sign rotating shaft assembly comprises a mounting frame 31 including two plates 32 each of which is dimensioned and shaped to fit snugly inside the supporting post 12. In the embodiment illustrated the plates are cross-shaped and have a central opening 34 (shown only in the lower plate) for the shaft 24 to pass through. The plates 32 are held in parallel spaced relationship in any suitable manner, e.g., by bending the ends of the arms into flanges 36 which are then joined together by welds 37. The flanges 36 are suitably tapped to'receive machine screws 38,.for example, flat head Allen screws, to secure the mounting frame 31 to the supporting post 12. The flange 30 of the ball bearing assembly is secured to the upper mounting plate 32 by means of machine screws 40, e.g., hexagonal head cap screws, with the cap l8 between them. The top 20 is provided with suitable openings (not shown) for shaft 24 and machine screws 40 and, if desired, a gasket or other water proofing material may be interposed between the flange 30 of the upper ball bearing and the top.20 of the cap to prevent water from seeping into the interior by capillary attraction. The flange 30 of the lower ball bearing is suitably fastened in similar manner by machine screws 40 to the lower mounting plate as shown in FIG. 1. A commercially available .ball bearing of the type suitable for this invention has a square flange 30 which may be located with respect to the cross-shaped mounting frame 31 as shown in FIG. 2, which takes advantage of the cruciform shape of the supporting post to receive the largest size bearing that can be used in relation to the size of the post. Suitable modification in the shape of the mounting frame 31, flanges 30, cap 18 and other parts will be made for other cross-sectional shapes of the supporting post indicated above.

Each of the bolts used for securing the bearings to the mounting plate preferably has a split washer 42 under the head so as to inhibit loosening of the bolt by vibration- Mounted near the lower end of the sign rotating shaft 2, which may be of smaller diameter below the second bearing 26, is an insulating slip ring spool 44 having slip rings 46 and 48 on the periphery thereof, as may be seen in FIGS. 2 and 4, so that these rings have no electrical connection with the shaft 2 or with each other.

The slip ring-brush assembly 4 also comprises a brush holder post 50 suitably secured to any suitable fixed member in the supporting post, e.g., to the lower mounting plate 32, for holding an adjustment link 52 and a brush assembly 53. The adjustment link 52 is slidable on and rotatable around the brush holder post 50 and an insulating rod 54 of the brush assembly 53 so that brushes 55 of the brush assembly 53 can be brought into contact with the slip rings 46 and 48 at a suitable angle, e.g., 90 to a tangent through the center line of the area of contact, and with proper pressure of the brush against the slip rings for good electrical contact. The link 52 must be held in this proper adjusted position on post 50 and rod 54, e. g., by set screws 56, of which only one is shown in FIG. 2, and they are preferably of the Allen type.

At the upper end of the sign rotating shaft 2 is a hub flange 58 suitable secured thereto, e.g., by an allen set screw 60. The hub flange 58 is provided with any suitable means for securing it to the sign structure.

As indicated above, where the sign is illuminated it is necessary to provide electrical power to it through the parts that rotate with the sign and this may be accomplished by means of an insulated electrical wire 62 having at least two conductors which are electrically connected respectively to the slip rings 46 and 48 in the manner indicated in FIG. 4. The wire 62 extends through a passage 64 in the sign rotating shaft 2 from which these conductors of wire 62 are insulated. The conductors of wire 62 may be suitably electrically connected to the illuminating devices in the sign. As seen in FIGS. 1 and 2, an insulated wire 66 is provided having the requisite number of electrical conductors, e.g., two marked 67 and 68 which are connected, respectively, to brushes 55. The two brushes are insulated from each other and they conduct the electrical power from a suitable source to which wire 66 is connected through the slip rings and electric wire 62 into the sign. If desired, a switch (not shown) may be installed between the source and the brushes for controlling the supply of electric power to the sign.

The friction clutch or torque limiter 7 includes a housing coupling 70 secured to the sign rotating shaft 2 below the slip ring spool 44, as seen best in FIG. 3. Any suitable means may be used to secure the coupling 70 to the shaft 2, e.g., a pin 72, passing through the coupling and the shaft as illustrated. A clutch plate 74 is suitably secured, e.g., by bolts 75, to the clutch housing and it is provided with a central opening for the hub 76 of an integral hub and pressure plate 77. The hub 76 has a circular recess 78 to receive one end of a shaft 79 which is keyed or otherwise fixedly mounted therein. The hub 76 is generally circular in cross-section, has an external thread 80 thereon but is flattened at 81 on opposite sides thereof so that an end wrench can be slipped over it to hold it against rotation. Two unbonded friction facings 82 in the form of apertured discs are rotatably mounted on the hub 76 between the clutch plate 74 and the pressure plate 77., A dished spring and lock washer 84 on hub 76 is pressed against plate 74 by a pressure adjusting nut 86 which can be screwed down to provide any degree of friction desired on the clutch plate 74. This adjustment may be effected with one end wrench on the flattened part 81 of the hub 76 and another end wrench on the pressure adjusting nut 86 which can be locked in proper adjusted position by any suitable means, e.g., an Allen set screw The electrical motor 5 for driving the sign rotating shaft 2 through suitable connections comprises a casing 90 that may be mounted in post 12 by means of a mounting frame 92 having a motor mounting disc 94 to which casing 90 is secured by any suitable means, e.g., hexagonal head cap screws 96 with underlying split washers 98 to prevent loosening of the screws by vibration. The mounting frame 92 includes two diametrically opposed spacers 100, each welded at one end to disc 94 and provided with a mounting bracket 102 welded or otherwise secured thereto which, as shown in FIG. 5, is bent so that the ends 104 just fit into the side channels 105 of post 12 (shown in section in FIG. 3) where they are secured by screws 106 in the lateral side walls or webs 107 of the channels 105.

An electrical conductor 110 is provided in the hollow supporting post 12 to bring electrical power from an external source through the post to the motor 5 and this conductor may be provided with a switch, (not shown), for controlling the operation of the motor in any desired way.

The speed reducing mechanism 6 is also mounted, e.g., by means of bolts 112, on the mounting frame 92 by means of a mounting disc 1 l4 suitably secured to the other end of spacers 100, e.g., by welding. The speed reduction mechanism is provided with an input shaft 116 and an output shaft 118. The drive shaft 120 of electrical motor 5 is provided with suitable means 122 for connecting it to the input shaft 116, e.g., by a connection including yielding material such as rubber. A suitable connector is the U. S. Rubber coupling 0325 F.

The speed reducing mechanism 6 may be of any suitable type but preferably is one in which the input and output shafts 116 and 118 rotate around the same axis. This is very desirable in order that the motor shaft 120, the input and output shafts 116 and 118 of the speed reducing mechanism 6, the shaft 79, the hub 76, the housing coupling 70 of the friction clutch or torque limiter 7, (where used), the sign rotating shaft 2 and all of the connections between these parts may be in axial alignment and rotate about a substantially common axis. Perfect axial alignment, which would be required if rigid connections were used between these shafts, is unnecessary since it is more economical to provide flexible couplings for most if not all of these connections but the in-line relationship of the parts is important in order to accomodate the drive unit in the hollow post. There are a number of commercially available speed reducing mechanisms which have the input and output shafts in alignment, including such mechanism utilizing the principle of internal planetary gearing such as illustrated in FIG. 6 comprising a ring gear 172a, a planet gear 1900, a crank shaft having a crank pin 116a rotatably mounted in the planet gear a and concentric therewith so that rotation of the planet gear around its own axis is at a substantially reduced speed with respect to the speed of the of the crank shaft around the axis of the ring gear. This type of speed reducing mechanism is quite satisfactory if the mechanism is protected against sudden shocks as can occur if a gust of wind strikes the sign and causes it to rotate. With the internal planetary type of gear reducing mechanism it is quite important to use a friction clutch to protect the mechanism against such sudden shocks. Another and preferred type of speed reducing mechanism is the epitrochoid planet gear-circular (pin) tooth sun gear combination such as shown in FIG. 7 in which there is an internal sun gear 172, a planet gear 188 having a crank shaft pin or an eccentric 162 mounted for rotation around the center or axis of the planet gear and a constant speed internal gearing mechanism comprising the planet gear or cycloid disc 188 and slow speed shaft pins 186. In this mechanism, the pins 186 of the slow speed shaft 118 are evenly spaced on a circle which is concentric to the axis of the ring gear 172. The pins 186 transmit the rotation of the planet gear by rolling internally on the circumference of bores 196 in each planet gear or cycloid disc 188, 190. The diameter of the bores 196, minus the diameter of the slow speed shaft pins 186, is equal to twice the eccentricity value of the crank shaft or eccentric 162, 164.

This mechanism smoothly transmits only the rotation of the planet gear 188, 190 around its own axis to the slow speed shaft. By using a planet gear having cycloidal shaped teeth 192, 194 and a ring gear 172 with circular shaped teeth or rollers 174, and the number of teeth of the planet gear being one less than that of the ring gear, a constant speed internal gearing mechanism is provided. This type of mechanism is available from Sumitomo Machinery Corp. of America and is known as a SM-Cyclo Drive. A typical construction of such a speed reduction mechanism is illustrated in FIG. 7 in which the input or high speed shaft 1 16 has mounted thereon a bearing 160 adjacent to the exposed end thereof, a first eccentric 162, a second eccentric 164 and a reduced end portion 166 to receive the inner race of a bearing 168 that is mounted in a manner soon to be described. Bearing 160 is supported in the high speed end shield 170 which is bolted to the fixed ring gear 172. The teeth of this ring gear comprise rollers 174 suitably journaled, as shown, in equidistant radial and angular relation around the entire inner surface of the ring 172. A slow speed end shield 176 is similarly bolted to the other side of ring gear 172 to form, with gear 172 and shield 170, a casing for the mechanism. Slow speed shaft 118 is mounted in shield 176 by a bearing 178 near the exposed end and a bearing 180 near the inner endthereof on which a pin wheel 184 is fixed. Pin wheel 184 is also provided with a central recess to receive and support the outer race of bearing 168. Pins 186 are secured in equal radial and angular distance to the face of wheel 184 to cooperate with the planet gears or cycloid discs 188 and 190 which have alternate cycloidal teeth 192 and hollows 194 on their peripheries and bores or holes 196 extending transverse ly through the discs to receive the pins v186. These pins are moved by engaging the walls of the holes 196 and to reduce friction the pins may comprise stub shafts and rollers or sleeves as shown. The cycloid discs 188 and 190 are rotatably mounted on eccentrics 162 and 164, respectively, preferably by means of roller or ball bearings 200. With this construction the ratio of angular velocity V of the output shaft 118 to the angular velocity V of the input shaft 116 is equal to 1 minus the number of rollers 174 in the sun gear 172, designated by S, divided by the number of teeth 192 in the planet gears 1 88 and 190, designated by P, i.e.,

Where S is l greater than P, the velocity ratio may be calculated from the equation V /V UP), the negative sign indicating that the shafts 116 and 118 rotate in opposite directions. The described mechanism has the distinct advantage of distributing any stress not to a few teeth, as in an internal planetary gear system, but to all of the pins 186 so that this type of mechanism is much less susceptable to damage from sudden shock than the internal planetary gearing system. Moreover, with sufficient torque applied to the slow speed shaft 118, the high speed shaft 116 can be driven which is not possible in planetary gear systems. This means that if the SM- Cyclo Drive is connected through flexible coupling 130 directly to shaft 2, instead of indirectly through a torque limiter or friction clutch 7, and a gust of wind strong enough to move sign 3 against the force of motor 5 strikes it, motor 5 may be stopped or actually reversed. By providing the motor with a thermal cutout 125 which opens the motor circuit when the motor rises in temperature, as it does when the motor is stalled or reversed, and automatically closes the circuit when the motor has cooled to a predetermined temperature, the use of a friction clutch may be avoided, if desired.

The flexible connection 8 may have any desired structure capable of providing an operative connection between the output shaft 118 of the speed reduction mechanism and either the sign rotating shaft 2 or the friction clutch 7, as the case may be. One suitable flexible coupling 130 comprises two universal joints connected together by a stub shaft and to the driven and driving shafts respectively. One joint 132 comprises a pair of bifurcated elements 133 and 134 pivoted respectively to opposite ends of a four-arm cross 135 in customary manner. Element 133 is suitably secured to the shaft to be driven, in this case shaft 79, e.g., by a pin 136. The other bifurcated member 134 of joint 132 issuitably secured to a stub shaft 137, e.g., by a pin 138. A similar universal joint is suitably secured by one of the bifurcated members 141 to the stub shaft 137 by a pin 142 while the other bifurcated member 143 is suitably secured to the output shaft 118 of the speed reduction mechanism 6, e.g., by a pin 144. Other forms of flexible connecting means may also be employed.

As indicated above, it is preferred to provide an access door 9 in the supporting post to permit inspection and repairs without having to take the post and sign down. For this purpose a length of part of the supporting post is cut away as illustrated in FIGS. 1 and 2. The post in this embodiment of the invention, being cruciform in cross section, may have the door comprise one of the side channels 105 and the lateral webs 107 of the two adjacent side channels as seen best in FIG. 2, which provides the maximum width of door for easy access to internal parts. In posts of other cross-sectional shapes similar access doors can be provided. This door may be suitably secured to the post by a piano type hinge 146 to permit the door to swing open and is provided with means to secure the door in closed position except when access to the interior for inspection or repairs is desired. The locking means to hold the door shut may take any desiredform. A satisfactory fastening device comprises a plurality of angle brackets 150 secured by one arm in any desired manner by bolts, welding or the like to the edge of the supporting post along the opposite side thereof from the hinge 146 and having in the other arm a tapped hole adapted to receive machines screws 152. Screws 152 may suitably be flat head Allen screws countersunk into the door. Other suitable fastening means may also be used, if desired.

In the embodiment of the invention shown in FIGS. 1, 2 and 5 it will be noted that the diameter of the motor 5 and the lateral dimensions of the mounting frame 92 are greater than the width of a side channel 105 and that they extend into the four side channels. This preferred structure takes full advantage of the available space within the post 12 for the motor 5 and mounting frame 92, as well as for the bearings 26 and associated flanges 30. The drive unit maybe mounted equally well, however, in circular, hexagonal, octagonal or square posts and the in-line arrangements of parts keeps the crosssectional dimensions small enough to be housed in posts of about usual diameter for large signs.

Although the invention has been described and illustrated in connection with the best embodiment of the invention presently known to the inventor, those skilled in the art will recognize that modifications and substitutions of the equivalents may be made without departing from the principles of the invention as set forth hereinabove.

What is claimed is 1. A drive unit for a rotatable sign comprising:

a. a vertical elongated hollow tubular support having an upper end;

b. a sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having means at its upper end adapted to be secured to a sign;

c. a mechanical speed reducing mechanism in said hollow support below said sign rotating shaft having an output element and an input shaft;

d. an electrical motor mounted in said hollow support below said speed reduction mechanism and having a shaft;

e. means operatively connecting said motor shaft to the input shaft of said speed reduction mechanism and the output element thereof to said sign rotating shaft; and

f. means closing the upper end of said hollow tubular support against ingress of water.

2. A drive unit for a rotatable electrically illuminated sign comprising:

a. a vertical elongated hollow tubular support having an upper end;

b. a hollow sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having (i) means at its upper end adapted to be secured to a sign, (ii) insulated slip rings secured thereto adjacent to he lower end thereof and (iii) an electric wire extending from each slip ring through said hollow shaft beyond the upper end thereof;

0. a speed reducing mechanism in said hollow support having an output element and an input shaft;

d. means operatively connecting said sign rotating shaft to said output element;

e. an electrical motor mounted in said hollow support and having a shaft;

f. means operatively connecting said motor shaft to said input shaft;

g. brushes mounted in said hollow support, each in engagement with one of said slip rings, for supplying electric power to said sign; and

h. means closing the upper end of said hollow tubular support against ingress of water.

3. A support and drive for a rotatable sign comprising a hollow post adapted to be mounted in upright position and a drive unit housed in the upper end of said hollow post, said drive unit comprising:

a. a motor mounted in said hollow post;

b. a speed reducing mechanism having an input shaft and an output element;

c. a friction clutch having a driven element and a driving element;

d. a rotatable main shaft journaled in bearings secured in the upper end of said hollow post, the upper end of said shaft extending beyond the upper end of said hollow post and being adapted for mounting a sign thereon;

. means connecting said motor to the input shaft of said speed reducing mechanism, the output element of the latter to the driven element of said friction clutch and the driven element of said clutch to said main shaft; and

f. means closing the upper end of said hollow post against ingress of water.

4. A support and drive as set forth in claim 3 in which said speed reduction mechanism is a cycloidal drive.

5. A support and drive for a sign comprising a vertical hollow post and a drive unit housed in the upper end of said hollow post, said drive unit comprising:

a. a motor mounted in said post with its shaft vertical;

b. a cycloidal drive speed reducing mechanism having an input shaft operatively connected to said motor shaft and an output shaft;

. a shaft journaled vertically in the upper end of said hollow post operatively connected to said output shaft at its lower end and with its upper end extending above the upper end of said post and having means on its upper end adapted to be connected to a sign, at least one of said operative connections being flexible whereby perfect alignment of the motor shaft with the journaled shaft is not necessary; and

d. means closing the upper end of said hollow post against ingress of water.

6. A drive unit as set forth in claim 5 in which said post includes a door that can be opened for inspection and maintenance of said unit and removably locked in closed position.

7. A support and drive for a sign comprising a hollow post adapted to be mounted in upright position and a drive unit housed in the upper end of said hollow post, said drive unit comprising:

a. a support frame mounted in said post;

b. a motor mounted on said support frame, said motor having a shaft;

c. a speed reducing mechanism mounted on said support frame above said motor, said mechanism having an input shaft operatively connected to said motor shaft and an output shaft;

d. a sign rotating shaft journaled vertically in the upper end of said post with its outer end extending beyond the upper end of said hollow post and having means at said outer end adapted to be connected to a sign;

e. a friction clutch having an output element and an input element, said output element connected to the inner end of said sign rotating shaft;

f. a universal joint connection between the input element of said clutch and the output shaft of said speed reducing mechanism, said motor shaft, input and output shafts and elements, and said sign rotating shaft being in substantial alignment; and

g. means closing the upper end of said hollow post against ingress of water.

8. A drive unit for a sign as set forth in claim 1 in which the hollow support is a post of cruciform cross section and the motor extends into the side channels thereof.

9. A drive unit for a rotatable sign comprising:

a. an elongated vertical hollow support;

b. a sign rotating shaft journaled in the upper part of said support with its outer end extending beyond the upper end of said post and having means at its said outer end adapted to be secured to a sign;

c. an electrical motor mounted in said hollow support and having a shaft;

d. a circuit for said motor including a thermal cut out to break the circuit when the motor temperature rises above a predetermined value and automatically to close the circuit when the motor temperature falls below a predetermined value;

e. a speed reduction mechanism in said hollow support of the epitrochoid planet gear-circular (pin) tooth sun gear combination type having axially aligned input and output shafts;

f. means operatively connecting said motor shaft to said input shaft;

g. means operatively connecting said output shaft to said sign rotating shaft; and

h. means closing the upper end of said hollow support against ingress of water;

said speed reduction mechanism and motor being adapted to yield to abnormal torque induced by strong winds on the sign without damage to said motor due to stalling or reversal because of said thermal circuit breaker and to rotate said sign again automatically when said abnormal torque is reduced.

10. A drive unit for a rotatable sign comprising:

a. a vertical elongated hollow tubular support having an upper end;

b. a sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having means at its upper end adapted to be secured to a sign;

c. a speed reducing mechanism in said hollow support below said sign rotating shaft having an output shaft and an input shaft;

d. an electrical motor and circuit therefor mounted in said hollow support below said speed reduction mechanism and having a shaft;

e. means operatively connecting said motor shaft to the input shaft of said speed reduction mechanism and the output shaft thereof to said sign rotating shaft, the axes of rotation of all said shafts being in substantial alignment;

f. means for protecting said motor from damage due to unusual resistance to rotation of said sign rotating shaft; and

g. means closing the upper end of said hollow tubular support against ingress of water.

11. A drive unit for a rotatable sign as set forth in claim 10 in which said motor protecting means is a friction clutch having axially aligned input and output elements connected between, to and in alignment with said output shaft of said speed reducing mechanism and said sign rotating shaft, respectively. 

1. A drive unit for a rotatable sign comprising: a. a vertical elongated hollow tubular support having an upper end; b. a sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having means at its upper end adapted to be secured to a sign; c. a mechanical speed reducing mechanism in said hollow support below said sign rotating shaft having an output element and an input shaft; d. an electrical motor mounted in said hollow support below said speed reduction mechanism and having a shaft; e. means operatively connecting said motor shaft to the input shaft of said speed reduction mechanism and the output element thereof to said sign rotating shaft; and f. means closing the upper end of said hollow tubular support against ingress of water.
 2. A drive unit for a rotatable electrically illuminated sign comprising: a. a vertical elongated hollow tubular support having an upper end; b. a hollow sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having (i) means at its upper end adapted to be secured to a sign, (ii) insulated slip rings secured thereto adjacent to he lower end thereof and (iii) an electric wire extending from each slip ring through said hollow shaft beyond the upper end thereof; c. a speed reducing mechanism in said hollow support having an output element and an input shaft; d. means operatively connecting said sign rotating shaft to said output element; e. an electrical motor mounted in said hollow support and having a shaft; f. means operatively connecting said Motor shaft to said input shaft; g. brushes mounted in said hollow support, each in engagement with one of said slip rings, for supplying electric power to said sign; and h. means closing the upper end of said hollow tubular support against ingress of water.
 3. A support and drive for a rotatable sign comprising a hollow post adapted to be mounted in upright position and a drive unit housed in the upper end of said hollow post, said drive unit comprising: a. a motor mounted in said hollow post; b. a speed reducing mechanism having an input shaft and an output element; c. a friction clutch having a driven element and a driving element; d. a rotatable main shaft journaled in bearings secured in the upper end of said hollow post, the upper end of said shaft extending beyond the upper end of said hollow post and being adapted for mounting a sign thereon; e. means connecting said motor to the input shaft of said speed reducing mechanism, the output element of the latter to the driven element of said friction clutch and the driven element of said clutch to said main shaft; and f. means closing the upper end of said hollow post against ingress of water.
 4. A support and drive as set forth in claim 3 in which said speed reduction mechanism is a cycloidal drive.
 5. A support and drive for a sign comprising a vertical hollow post and a drive unit housed in the upper end of said hollow post, said drive unit comprising: a. a motor mounted in said post with its shaft vertical; b. a cycloidal drive speed reducing mechanism having an input shaft operatively connected to said motor shaft and an output shaft; c. a shaft journaled vertically in the upper end of said hollow post operatively connected to said output shaft at its lower end and with its upper end extending above the upper end of said post and having means on its upper end adapted to be connected to a sign, at least one of said operative connections being flexible whereby perfect alignment of the motor shaft with the journaled shaft is not necessary; and d. means closing the upper end of said hollow post against ingress of water.
 6. A drive unit as set forth in claim 5 in which said post includes a door that can be opened for inspection and maintenance of said unit and removably locked in closed position.
 7. A support and drive for a sign comprising a hollow post adapted to be mounted in upright position and a drive unit housed in the upper end of said hollow post, said drive unit comprising: a. a support frame mounted in said post; b. a motor mounted on said support frame, said motor having a shaft; c. a speed reducing mechanism mounted on said support frame above said motor, said mechanism having an input shaft operatively connected to said motor shaft and an output shaft; d. a sign rotating shaft journaled vertically in the upper end of said post with its outer end extending beyond the upper end of said hollow post and having means at said outer end adapted to be connected to a sign; e. a friction clutch having an output element and an input element, said output element connected to the inner end of said sign rotating shaft; f. a universal joint connection between the input element of said clutch and the output shaft of said speed reducing mechanism, said motor shaft, input and output shafts and elements, and said sign rotating shaft being in substantial alignment; and g. means closing the upper end of said hollow post against ingress of water.
 8. A drive unit for a sign as set forth in claim 1 in which the hollow support is a post of cruciform cross section and the motor extends into the side channels thereof.
 9. A drive unit for a rotatable sign comprising: a. an elongated vertical hollow support; b. a sign rotating shaft journaled in the upper part of said support with its outer end extending beyond the upper end of said post and having means at its said outer end adapted to be secured to a sign; c. an electrical motor mounted in said hollow support and having a shaft; d. a circuit for said motor including a thermal cut out to break the circuit when the motor temperature rises above a predetermined value and automatically to close the circuit when the motor temperature falls below a predetermined value; e. a speed reduction mechanism in said hollow support of the epitrochoid planet gear-circular (pin) tooth sun gear combination type having axially aligned input and output shafts; f. means operatively connecting said motor shaft to said input shaft; g. means operatively connecting said output shaft to said sign rotating shaft; and h. means closing the upper end of said hollow support against ingress of water; said speed reduction mechanism and motor being adapted to yield to abnormal torque induced by strong winds on the sign without damage to said motor due to stalling or reversal because of said thermal circuit breaker and to rotate said sign again automatically when said abnormal torque is reduced.
 10. A drive unit for a rotatable sign comprising: a. a vertical elongated hollow tubular support having an upper end; b. a sign rotating shaft having upper and lower ends journaled in said hollow support with the upper end of said shaft extending above the upper end of said hollow support and having means at its upper end adapted to be secured to a sign; c. a speed reducing mechanism in said hollow support below said sign rotating shaft having an output shaft and an input shaft; d. an electrical motor and circuit therefor mounted in said hollow support below said speed reduction mechanism and having a shaft; e. means operatively connecting said motor shaft to the input shaft of said speed reduction mechanism and the output shaft thereof to said sign rotating shaft, the axes of rotation of all said shafts being in substantial alignment; f. means for protecting said motor from damage due to unusual resistance to rotation of said sign rotating shaft; and g. means closing the upper end of said hollow tubular support against ingress of water.
 11. A drive unit for a rotatable sign as set forth in claim 10 in which said motor protecting means is a friction clutch having axially aligned input and output elements connected between, to and in alignment with said output shaft of said speed reducing mechanism and said sign rotating shaft, respectively.
 12. A drive unit for a rotatable sign as set forth in claim 10 in which said motor protecting means includes a circuit for said motor having a thermal cut out to break the circuit when the motor temperature rises above a predetermined value and automatically to close the circuit when the motor temperature falls below a predetermined temperature. 